Vitamin A compounds have heretofore been clinically tested in certain selected areas of dermatology. For example, a large number of dermatologists have experimentally treated certain diseases such as, for example, ichthyosis, Darier's disease, psoriasis and other keratoses by the topical administration of vitamin A. In addition, some keratoses such as, for example, ichthyosis vulgaris and ichthyosiform erythrodermia have been experimentally treated by the systemic administration of vitamin A.
Inconsistent results obtained with vitamin A palmitate utilized both locally and systemically has caused some workers, notably Stuttgen, to experiment with attempts to influence keratoses locally with vitamin A acid. He reported in Dermatologica 124: 65-80 (1962) that positive results were obtained with ichthyosis vulgaris, ichthyosiform, erythrodermia and also with three cases of senile keratoses. More recently, other workers have realized therapeutic success with locally applied vitamin A acid in treating lamellar ichthyosis, psoriasis and epidermolytic hyperkeratoses. It has now been discovered that 13-cis vitamin A acid or a pharmaceutically acceptable salt thereof is particularly effective systemically in the prophylaxis of certain epithelia carcinomas and premalignant conditions of the epithelial cells.
The epithelium forms the outer protecting surface of the body and all glands, furnishes important parts of the sense organs and lines the walls of the internal cavities. It is best classified in terms of the shape of the epithelial cells and their arrangement in epithelial sheets. Although the cells may vary in shape with movement of the epithelium, they are mainly flat, i.e. squamous cells, cuboidal, or columnar in appearance. Sheets of these cells are variously classified as simple where a single layer of cells exists or stratified where many layers exist. Epithelial cells may have on their free surface motile, hairlike processes called cilia or smaller, non-motile processes constituting a brush border and can be cornified or not. The epithelial cells perform an extremely important function in the process of metabolism in that all substances absorbed from the outside medium and eliminated to the outside medium must pass through them. The present invention is directed to cancers affecting these vital cells.